1. Technical Field
The present invention relates to a thermal detector, a thermal detection device, and an electronic instrument or the like.
2. Related Art
Known thermal detection devices include pyroelectric or bolometer-type infrared detection devices. An infrared detection device utilizes a change (pyroelectric effect or pyroelectronic effect) in the amount of spontaneous polarization of a pyroelectric material according to the light intensity (temperature) of received infrared rays to create an electromotive force (charge due to polarization) at both ends of the pyroelectric body (pyroelectric-type) or vary a resistance value according to the temperature (bolometer-type) and detect the infrared rays. Compared with a bolometer-type infrared detection device, a pyroelectric infrared detection device is complex to manufacture, but has the advantage of excellent detection sensitivity.
A cooling device is usually not included in the structure of a thermal detection element. It is therefore necessary to adopt a structure in which the element is housed in an airtight package, the element is placed in a reduced-pressure environment and thermally separated from the substrate or the peripheral layers, and heat evolved by received light (infrared rays or other light) is kept as much as possible from diffusing into the surrounding area. An example of an effective means of preventing prevent heat from dissipating into the substrate, and of suppressing reductions in the detection characteristics of the thermal detection element, is to employ a structure in which a cavity for thermal separation is provided between the substrate and the thermal detection element (see Japanese Laid-Open Patent Publication No. 2000-205944 and Japanese Laid-Open Patent Publication No. 2002-214038, for example). Japanese Laid-Open Patent Publication No. 2000-205944 discloses a thermal infrared array sensor which has a cavity for thermal separation, and Japanese Laid-Open Patent Publication No. 2002-214038 discloses a pyroelectric infrared detection element which has a cavity for thermal separation.